Beam Position Monitors

The BPMs must be placed at crucial points. They are located close to the quadrupoles (the most important source of COD) or close to the sextupoles (COD in the sextupole creates a tune shift which can deteriorate the nominal dynamic aperture) and at both ends of each straight section (Insertion devices locations where the correction is the most important).

There are a total of 226 button BPMs used for both slow and fast orbit correction in PETRA III storage ring. Out of 220, 156 BPMs are placed in the Old Octant and the rest 70 are installed in the New Octant.

Considering the alignment errors, girder fixers, it is foreseen that the readings errors will be higher in the old octant rather than new octant. The requirement of submicron beam stability imposes the tight reading errors in the BPMs on either side of insertion devices. With respect to required reading errors the monitors are divided into 3 categories as follows:

BPM : Monitors mostly in the Old Octants (Normal)

BPMM: Monitors in the new Octant (Medium)

BPMF: Monitors on either side of the IDs (Fast)

Monitor Misalignment Errors (rms values)

The following rms misalignment (say including reading resolutions) errors (truncated at 2s) are considered during the slow orbit simulation studies.

For Slow Orbit Correction Scheme

Monitors Types	Horz. Reading Errors(mm)	Vert.. Reading Errors(mm)
BPM	200	200
BPMM	200	200
BPMF	200	200

Monitor Reading Errors (Resolution : rms values)

For Fast Orbit Correction Scheme

Monitors Types	Horz. Reading Errors(mm)	Vert.. Reading Errors(mm)
BPM	10	10
BPMM	2	0.5
BPMF	2	0.2

The monitors mostly placed near high beta functions near quadrupoles. In the old octant there are placed near horizontally defocussing quadrupoles. The following figures show the Phase Advances in Horizontal and vertical plane between the Monitors:

The following figures show Phase Advances between the Monitors at different DBA cells:

The location of monitors  in the DBA cell is shown in the following figure. There are 7 BPMs per cell.

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